1. Field of the Invention
The present invention relates to the field of engine making and, more particularly, it relates to a method of controlling the revolution of the drive shaft of an external combustion engine and to Russin external combustion engine.
This invention can be used most advantageously in reciprocatiing heat engines.
2. Description of the Prior Art
In view of the energy crisis affecting many countries and a catastrophic pollution of the atmosphere of large cities with exhaust gases of the existing internal combustion engines, one of the most urgent problems of today appears to be that of developing an engine having on its drive shaft a constant maximum torque independent of the engine r.p.m., featuring a stability and uniformity of the drive shaft revolution over a wide range of from zero to the maximum value on the order of 5,000 r.p.m. without using a flywheel and r.p.m. governor, fired with practically any readily available fuel and polluting the atmosphere with waste gases but slightly, featuring a high power at small weight and overall dimensions, exhibiting a high efficiency, reliability, response and operating economy, as well as characterized by simplicity of control (requiring no gear boxes and clutch gears) when mounted on a transport vehicle.
A serious drawback of internal combustion engines is the non-uniformity of the drive shaft revolution, due to the principle of their operation. In order to reduce the non-uniformity of the drive shaft revolution, use is made of a rather massive flywheel (15-20% of the engine weight), which results in lower engine response and efficiency, as well as in greater weight and overall dimensions of the engine.
Another disadvantage of said engines resides in a strong dependence of the drive shaft torque upon its r.p.m. The higher the torque, the greater the drive shaft r.p.m. value, and vice versa. Therefore, when using such an engine in a transport vehicle, in case low r.p.m. and high torque are required on the drive shaft upon smooth starting, a gear box and clutch gear should be used. A clutch gear is further required because it is impossible to start an internal combustion engine under load.
It should also be noted that high-power internal combustion engines need a special r.p.m. governor, for the engine may start racing. However, such governor varies the drive shaft r.p.m. value by affecting the fuel consumption, i.e., it reduces the fuel flow rate to reduce the drive shaft r.p.m., which results in a lower torque.
Therefore, internal combustion engines fail to ensure stability and uniformity of revolution of the drive shaft, as well as a constant drive shaft torque, over a wide range of r.p.m. values from 0 to .eta..sub.max.
There are also known in the art external combustion engines, for example, reciprocating heat engines which, as compared to internal combustion engines, feature a somewhat more uniform revolution of the drive shaft, higher efficiency, require no expensive fuel and discharge less atmosphere-polluting waste gases.
However, they also suffer from a number of disadvantages, of which the major ones include the non-uniformity and instability of the drive shaft revolution, due to a strong dependence of the speed of the drive shaft rotation upon the pressure of working fluid and load; a low drive shaft torque at low r.p.m.; a limited range of r.p.m. values; the need to use a flywheel and r.p.m. governor; low response; impossibility of rapid reversing and emergency stopping.
The non-uniformity and instability of the drive shaft rotation are due to the fact that prior art reciprocating heat engines have a direct positive mechanical feedback with respect to the piston position. This positive feedback causes the engine to race upon an increase in the pressure of the working fluid supplied to the valve distributor from a source and the non-uniformity of the drive shaft rotation at low r.p.m.
The afore-described disadvantages of prior art reciprocating heat engines resulted in their restricted use in transport vehicles.
There are further known in the art d.c. electric motors which have a higher uniformity of the drive shaft rotation as compared with external combustion engines. However, these latter motors suffer from a series of drawbacks restricting their use in transport vehicles. The first one of said drawbacks consists in the instability of the drive shaft torque over a wide range of r.p.m. values, due to the fact that the drive shaft r.p.m. and torque are directly proportional to the current in the armature winding of an electric motor. As a result, the torque developed on the engine shaft upon low r.p.m. when starting a transport vehicle has the minimum value whereas the desired drive shaft torque for smooth starting of a vehicle should be the maximum one. The second drawback resides in the instability of r.p.m. values of the electric motor drive shaft under conditions of direct current upon the variation of load applied to the drive shaft. The third one of said drawbacks consists in that it is impossible to stop such electric motors in a preset position of the drive shaft and reverse them instantaneously.
There is known a method of controlling the drive shaft rotation of an external combustion reciprocating engine, as well as an external combustion reciprocating engine such as steam engine (cf., N. V. Inozemtsev, Kurs teplovykh dvigatelei-A Course of Heat Engines, Oboronghiz Publishers, Moscow, 1954, p. 314, FIG. 343).
The prior art controlling method consists in the following.
First, a control signal is shaped for a switching member and converted to mechanical motion of an actuating member. Then, said mechanical movement of the actuating member is converted via converter to revolution of the engine drive shaft. After that, there is shaped a mechanical signal proportional to the sine (cosine) of the drive shaft angle of turn, by means of a second converter of the shaft revolution to the reciprocation of a positive mechanical feedback link which shapes the control signal for said switching member.
The control signal value is, in the general case, a variable sign and the shape of said signal at various loads, working fluid pressures etc. can be arbitrary, viz.: trapezoidal, triangular, truncated sine curve, parabolic, hyperbolic, etc. The control signal frequency is equal to the actual drive shaft r.p.m. value and varies with the load on the drive shaft and the working fluid pressure.
A reciprocating steam engine designed to accomplish said prior art method comprises an actuating cylinder in which a piston is mounted for reciprocation, said piston serving as the actuating member. The piston rod is coupled with a crank gear of the engine drive shaft, which serves as the converter of the actuating member reciprocation to the engine drive shaft revolution. The piston divides the cylinder into two cavities namely, a rodless cavity and a rod cavity. Each one of said cavities communicates with the steam source via valve distributor serving as the switching member. The engine drive shaft is rigidly coupled with a second crank gear serving as the converter of the drive shaft revolution to the reciprocation of a bar serving as positive mechanical feedback and articulated with its one end to the second crank gear and with its other end--to the distributor valve.
Inasmuch as the drive shaft revolution depends upon the presence of positive mechanical feedback between the drive shaft and valve, such revolution is, in principle, an unstable one, which results in the engine racing under conditions of high working fluid pressure and in the nonuniformity of rotation under conditions of low working fluid pressure. This calls for the provision of an r.p.m. governor and rather bulky flywheels, which limits the range of the drive shaft r.p.m. values and affects the engine response.
As a result of a high non-uniformity of the drive shaft rotation, said prior art method fails to ensure a constant drive shaft torque, this bringing about the emergence of inertia loads on the drive shaft which, in turn, calls for greater weight and larger overall dimensions of the engine because of strength requirements.
According to such method, the r.p.m. values of the engine drive shaft are adjusted by varying the working fluid pressure. This results in a lower torque at low r.p.m., which calls for the use of gear boxes and clutch gears when mounting such an engine on a transport vehicle, which brings about a heavier weight, more complicated structure, high mechanical losses and a lower efficiency.
In addition, since the prior art engine has positive mechanical feedback, it is incapable of varying the working fluid flow rate with load, which affects the operating economy of the engine. For the same reason, the engine cannot be momentarily stopped or reversed.
Due to the presence of the positive mechanical feedback link, the prior art method fails to ensure the stability and uniformity of the engine drive shaft rotation over a wide range of r.p.m. values at a constant shaft torque, as well as a single-valuedness of the actual r.p.m. value of the drive shaft and a preset r.p.m. value upon variation of the load applied to the shaft and the working fluid pressure.